Explosion proof plug and socket



Jan- 27, 1953 J. G. HOWARD ,ETAL 2,626,974

EXPLOSION PROOF PLUG ANO-SOCKET i Filed Sept. 16, 1949 2 SHEETS-SHEET l EM/L/m mig-5 Jan. 27, 1953 J. G. HOWARD ET A1. 2,6269974 EXPLOSION PROOF PLUG AND SOCKET Fild Sept. 16. 1949 2 SHEETS-SHEET 2 Z- fm2/*E17 D1-'.5 John @Howard Patented Jan. 27, 1953 EXPLOSION PROOF PLUG AND SOCKET John G. Howard and Philip S. Rockwell, Chicago, Ill., assignors to The Pyle-National Company, Chicago, Ill., a corporation of New Jersey Application September 16, 1949, Serial No. 116,025

6 Claims.

This invention relates generally to an electric plug and socket structure and more particularly relates to a so-called explosion-proof fitting incorporating a novel delayed action structure therein whereby a momentary time delay may be manually introduced into the manipulation of telescopically related plug and socket elements.

According to the general features of the present invention, a plug member is provided which is movable axially rectilinearly out of a socket member having terminals situated at the endl of arctight passages. The socket member carries a stop element which, in one preferred embodiment, takes the form of a ring which may be slidably mounted on the socket member and movable on a substantially lateral or radial plane relative to the axis of the plug and socket members. The plug member is provided with suitable fiat or slotted portions to define shoulders that cooperate with the stop member and prevent axial withdrawing movement of the plug member after the terminals are separated and before the plug and socket members are separated. The stop member can then be moved 4laterally or radially, whereupon further straight-line withdrawal of the plug member from the socket member may be permitted. Polarizing means may be provided between the plug and socket members to Amaintain these elements in a predetermined alignment.

-Most explosion-proof plug and socket structures heretofore provided have been constructed in accordance with designs which necessitate the employment of a rotatable locking member or zigzag detent means requiring twisting or relative rotative lmotion between plug and socket components in order that a suitable time delay be provided for rendering the plug and socket fitting explosion-proof.

An object of the present invention is therefore, to provide an electric plug and socket adapted for use in hazardous locations wherein all necessity for relative rota-tive motion between the plug and socket components is completely eliminated.

A further object of the present invention is to provide an electric plug and socket structure suitable for use in hazardous locations whereby a suitable time delay for rendering the plug and socket fitting explosion-proof may be accomplished by manual operation of a simple stop element movable in the fashion of a reciprocatory plunger.

Many other features, advantages and additional objects of the present invention will become 4manifest to those versed in the art upon making reference to the detailed description which follows and the annexed sheets of drawings, in which a preferred embodiment of the present inventionis shown.

On the drawings:

Figure 1 is a cross sectional View with parts in elevation and with parts broken away of an electric plug and socket according to the present invention;

Figure 2 is a cross sectional view with parts in elevation and with parts broken away taken on line II-II of Figure 1;

Figures 3 and 4 are fragmentary cross sectional views of the time delay mechanism incorporated in the electric plug and socket according to the present invention showing steps in a typical operational sequence; and

Figures 5 and 6 show the steps of a typical operational sequence of a modified electric plug and socket according to the present invention.

As shown on the drawings:

Referring to Figures l and 2, the electric plug and socket of the present invention is shown as including a socket member indicated generally by the reference numeral Ill, a plug member indicated generally by the reference numeral II and a stop member I2 for stopping the axial withdrawing movement of the plug in a manner which will be described in further detail hereinafter.

The socket member I Il includes a generally tubular housing I3 which may be made of metal and which preferably defines a suitable bore with internal shoulders therein for seating a sub-as- Sembly of electrical elements. It will be understood that the housing I3 may also be provided with suitable connection means on one end thereof for attachment to a junction box or other point of attachment as may be appropriate for various types of installations in hazardous environments likely to include dangerous quantities of explosive mixtures.

In this particular embodiment, a suitable pluglike receptacle I4 made of an electrically nonconductive material and being of a generally cylindrical form with an annular shoulder Illa on one end thereof may be positioned within the socket housing I3 and rmly aligned therein by means of the internal shoulder defined by the socket housing I3. A snap ring I6 may be provided to t in a suitable indentation dened by the bore of the socket housing I3 to lock the receptacle I4 in place.

The receptacle I4 is provided with a plurality of radially spaced arc-tight passages indicated generally by the reference numeral I'I. The arctight passages may be provided with a slight tapered counterbore at the ends thereof as at I'Ia so as to provide a finding area or locating area for male electrical elements, The arc-tight passages may be further counterbored internally to receive conventional female terminals I8 therein. Suitable end caps I9 may be provided for the terminals I 8 in the form of reduced diameter` portions adapted to receive a receptacle cap 20 in iitted assembly thereon. The receptacle cap 2G is held on the receptacle I by means of a fastener 2I.

One of the terminals i8 carried by the receptacle I4 may act as a ground terminal and therefore may be provided with a grounding wire 22 which is suitably connected to the socket housing I3 of the socket member Iii. It will be understood that such ground connection may be effected in other conventional manners, for example, a spring wire attached to the terminal I8 may be arranged to Contact the housing I3 at the locale between the shoulder portion Illa of the receptacle Ifi and the housing i3.

The socket housing I3 may be provided with suitable means for retaining a sealing waxyor similar compound in the end thereof, for example, as shown in this particular embodiment, the socket housing I3 has an annular groove 23 formed therein so that the entire end of the socket housing may be filled with a sealing wax, thereby enclosing the exposed ends oi the terminals. It will also be understood that suitable conductor leads may be provided and connected to each of the electric terminals i3 via the end caps I9.

The plug member II may be provided with an insulation shell 2li which is seated in one end of the plug member II. A plug body 23 made of electrically non-conductive material is also provided having a cap portion 25a and in which may be rmly assembled a plurality of prong-like male electrical terminal elements indicated by the reference numeral 2.

It will be noted that one ci the male terminals 2l may be of somewhat greater length than the others so as to serve the function of a ground terminal whereby the ground terminal will be the iirst to complete electrical Contact and the last to break contact.

The plug body 25 may be provided with a shallow longitudinal groove 2Gb in order to seat a locating pin 28 which is operative to keep the plug body 26 from rotating within the plug member II. Polarizing means may also be provided between thesocket housing I3 and the receptacle I4.

The plug member ii is provided with a generally tubular housing 23 which is preferably made of metal. As may clearly be seen on the drawings, the plug housing may be provided with recessed ila-ts formed on spaced diametrically opposed portions on its peripheral surface.

Referring particularly to Figure l, it will be noted that the lower portion of the plug housing 29 is provided with a rather lengthy ila-t indicated by the reference character' 23a which is terminated at one end by an annular shoulder 3i) and at the other end by a shoulder 35 donned by the normal peripheral portion of the plug housing which has not been removed to form the iiat 29a.

On the other side of the shoulder 3E, another flat 29h is defined which extends to thc end of the plug housing 2S.

Diametrically opposed from the shoulder 33 and flats 29a and 231i is an additional flat 23o. The at 23o is oi a limited length and terminates in shoulders defined by the normal peripheral portion of the tubular plug housing 25:.

As will be evident in the operational descrip* tion which is to follow, the location of the shoulder 35 and the at portions 29a, 29D and 29o are all predetermined so that a definite nxed relationship exists between the longitudinal or axial spacing of the various plug and socket components with respect to the axis of the plug member' I I and the socket member I0.

Referring now to Figures l and 2, the stop member i2 and its related elements may be described. The stop member I2 takes the general configuration of a ring with a central aperture I2a. A pair of projecting tabs 3i and 32 extend radially outward of the main body portion of the stop member- I2. Each of the tabs 3I and 32 extends into the aperture I2a to form a flattened portion 3Ia and 32a, respectively, and is further provided with an appropriate slot 3Ib and 32h, respectively, through which may extend a shoulder head screw 33. A suitably aperture, flanged retaining ring 3d may be provided to snugly surround the end of the socket housing I3 of the socket member I0 and is arranged to cooperate with the shoulder head screws 33 to retain the stop member I2 inslidable relation with the socket member lil.

The tab'32 may bel slightly longer than the tab 3| and may be bent over so as to provide a buttonlike operating portion as indicated at 32e.

If desired, appropriate bosses 36 may be provided on the stop member I2 and the socket housing I3 so as to seat a, small resilient member such as a coil spring 3'I therebetween. By virtue of such a provision, the stop member I2 may be normally biased towards an upper position.

Polarizing means may be provided between the socket member I0 and the plug member II so as to insure proper pre-alignment of the terminals I8 and 21 as well as to maintain alignment of the plug and socket members during relative movement thereof. In the present embodiment, the polarizing means takes the form of a, bead and groove structure, a bead 38 being provided in the inside bore of the socket housing I3 and a cooperating groove 39 being formed longitudinally in the wall of the plug housing 29 (Figure 2).

When the plug member II is completely inserted in the socket member I0, the male terminals 27 are completely seated within the arctight passages I'I so that electrical contact is made along the entire length of the female terminals I8. In this position, the annular shoulder 30 may be snugly seated up against the retaining ring 34.

It may be noted that the plug member is not locked in closed Contact position within the socket member and any extraordinary strain placed on a conductor leading to the plug member II will cause the plug member II to be partially withdrawn from the socket member I0, at least to the extent that the electrical terminals of the plug and socket members will be separated. It is desirable to provide this switching effect as a safety measure since it is quite possible that a small vehicle or a careless workman forcibly engaging and parting a conductor leading to an explosion-proof plug and socket as herein described would inadvertently create an explosion hazard ii the electrical contacts were to remain joined and current ilow was not interrupted to the conductor. It will be apparent that this feature also permits the structure to be employed as a switch.

Referring now particularly to Figures l, 3 and 4, the operational sequence of a withdrawal movement will be described particularly with respect to how a momentary time delay may be manually introduced into the manipulation of the telescopically related plug and socket elements.

When the plug member I I is fully inserted into the socket member I0, the stop member I 2, being normally biased to an upper position by the resilient member or spring 3'I has the flattened portion 3Ia of the tab 3i riding up against the ilat 28a of the plug housing 29 or in near proximity thereto. Thus, when the plug member II is partially withdrawn to the position shown in Figure 1, the stop member I2 will engagingly abut the shoulder 35 which, in effect, rises up between the at portions 29a and 29h of the plug housing 29. Further withdrawal movement of the plug member II is thereby precluded temporarily. It should be noted that, in this position, the terminals are separated but the plug terminals 2l have not left the arc-tight passages II.

In order to permit the further withdrawal of plug member II from the socket member I0, the stop member I2 may be depressed against the bias of the resilient member or spring 3l so that the tab 3l of the stop member I2 will clear the shoulder 35. It should be noted that the movement of the stop member I2 is generally lateral or radial relative to the axis of the plug and socket members. In order that the movement of the stop member I2 be accommodated, the flattened portion'32a of the tab 32 formed on the top part of the stop ring I2 finds a clearance in the recess provided by the flattened portion 29clocated diametrically opposite the shoulder 35.

Thus, after the stop member I2 is moved radially further withdrawal movement of the plug member II is permitted, as shown in Figure 3, until such time as the ilattened portion 32a of the tab 32 on the stop member I2 engages the shoulder presented by the terminating portion of the iiattened portion 29e.

In order to again permit further withdrawal movement of the plug member I I from the socket member I0, the stop member I2 must be released so that the flattened portion 3Ia of the tab 3! on the bottom portion of the stop ring I2 may again move upwardly toward the flattened portion 29h of the plug housing 29 and the attened portion 32a of the tab 32 on lthe upper portion of the stop ring I2 will clear the shoulder presented by the end of the attened portion 29o, thereby permitting complete Withdrawal of the plug member I I from the socket member I0. This phase of operation is shown in Figure 4.

It will be understood that any arc or flame drawn between the terminals I8 and 2l' will be cooled below ignition temperatures before the plug terminals 21 leave the arc-tight passages il.

Attention is invited to the fact that a particularly advantageous feature of the arrangement just described lies in the fact that all necessity for producing a relative rotative motion between plug and socket components as has been necessary in most explosion-proof plug and socket ttings heretofore provided has been completely eliminated and a suitable time delay for rendering the plug and socket tting explosion-proof is accomplished merely by a Simple manual actuation of a plunger-like stop member.

Referring now to Figures 5 and 6 a slightly modied form of an electric plug and socket incorporating the principles of the present invention is shown in two positions of a typical withdrawal sequence. In this form, the plug housing 2%' is provided with a flat portion as at 48 which difers from the ilat portions 29a and 22h provided on the plug housing 29 in that no separate shoulder is provided but the flat portion is medially spaced so as to terminate near the open end of the plug housing 29 in a shoulder 4I presented by the normal peripheral wall portion of the generally tubular plug housing.

Located diametrically opposite the flattened portion 4I) and the shoulder 4I is a flattened portion 42 which, unlike the flattened portion 29o, does not take the form of a slot-like at, but extends completely to the open end of the plug housing 29.

- The remainder of the plug and socket structure shown in Figures 5 and 6 is exactly similar to that provided in Figures 1, 2, 3 and 4 and corresponding reference numerals have been provided for the sake of orientation.

In eilecting a withdrawal movement of the modified fitting the stop member I2' will engage the shoulder 4I when the plug member I I is partially Withdrawn from the socket member III' so that the terminals are separated but the plug terminals 21 are still within the arc-tight passages I 'I. The stop vmember I2' is then depressed into the recess presented by the flattened portion 42 so as to clear the shoulder 4I and further withdrawal movement is permitted as shown in Figure 6.

It will be evident that the principles of this invention may be incorporated into other design applications than those herein illustrated by way of preferred embodiment. For example, the shoulder 35 and the corresponding diametrically opposed flat 29o may be duplicated at spaced intervals along the length of the plug member I I so as to comprise a plurality of shoulders 35 and a plurality of corresponding diametrically opposed ilats 29C. In this manner, the manual synchronization necessary to eiect a withdrawal movement would result in the introduction of successive momentary time delays, the additive or cumulative effect of which may be desirable for the particular use to which electric plug and socket may be adapted.

It will be evident that we have described an improved Yelectric plug and socket fitting incorporating a novel delayed action structure whereby a momentary time delay may be introduced manually into the manipulation of telescopically related plug and socket elements.

While a person skilled in the art might suggest various minor modifications to the structure herein described by way of preferred embodiment and illustrative example only, it should be understood that we do not propose to be limited to the precise details herein set out for the sake of clarity but Wish to embrace within the scope of this patent all such modications as reasonably and properly come within the scope of our invention.

We claim as our invention:

l. In an electric plug and socket apparatus, a socket member having passages formed therein, socket terminals in said passages, a plug member having plug terminals received in said passages and coacting with said socket terminals, said plug member being movable into and out of said socket member, latch means cooperating between said plug and socket members and including a movable stop member mounted on one of said members for movement relative to the other of said members, said stop member and said other of said members having a plurality of latch shoulders formed thereon, a rst pair of said latch shoulders confronting one another for temporarily blocking the withdrawal of said plug member after the plug and socket terminals are separated but before the plug terminals are withdrawn from said passages and a second. pair of said latch shoulders confronting one another for temporarily blocking withdrawal of said plug member a second time after a further partial withdrawal from said socket member, said stop member being selectively actuated to relatively displace said latch shoulders out of blocking relation.

2. A plug and socket construction comprising, axially telescoping plug and socket members having coacting terminals, a ring shaped stop member cooperating between said plug and socket members, guide means on the outermost of said plug and socket members confining said stop member for movement relative to the innermost of said members, said stop member and said innermost member having a plurality of latch shoulders formed thereon, a first pair 0f said latch shoulders confronting one another for temporarily blocking the axial separation of said plug and socket members after a partial separation, a second pair of said latch shoulders confronting one another for temporarily blocking the axial separation of said plug and socket members after a further partial separation, said stop member being selectively actuated to displace said latch shoulders relative to one another each time the separation of the plug and socket members is blocked.

3. A plug and socket construction comprising, axially telescoping plug and socket members having coacting terminals, a ring shaped stop member cooperating between said plug and socket members, guide means on the outermost of said plug and socket members confining said stop member for movement relative to the innermost of said members, continuous biasing means between said outermost member and said stop member urging said stop member in one direction, said stop member and said innermost member having a plurality of stop shoulders formed thereon, a first pair of said shoulders confronting one another for temporarily blocking the axial movement of said plug and socket members after a partial separation, a second pair of said shoulders confronting one another for temporarily blocking the axial movement of said plug and socket members after a further partial separation, said stop i member being moved against the biasing means to relatively displace said first shoulders out of confronting blocking relation and beingr moved by said biasing means upon release to relatively displace said second shoulders out of confronting blocking relation.

4. A plug and socket construction comprising, axially telescoping plug and socket members having coacting terminals, a ring shaped stop member cooperating between said plug and socket members, guide means on the outermost of said plug and socket members confining said stop member for movement relative to the innermost of said members, continuous biasing means between said outermost member and said stop member urging said stop member in one direction, said stop member and said innermost member having a plurality of stop shoulders formed thereon, a first pair of said shoulders confronting one another for temporarily blocking the axial movement of said plug and socket members after a partial separation, a second pair of said shoulders confronting one another for temporarily blocking the axial movement of said plug and socket members after a further partial separation. said stop member being moved against the biasing means to relatively displace said rst shoulders out of confronting blocking relation and being moved by said biasing means upon release to relatively displace said second shoulders out of confronting blocking relation, said stop member having a bent over peripheral flange portion spaced radially outwardly of the outermost member and forming a manual actuating handle for moving said stop member against the biasing means.

5. A plug and socket construction comprising, axially telescoping plug and socket members having coacting terminals, a ring shaped stop member cooperating between said plug and socket members, guide means on the outermost of said plug and socket members confining said stop member for movement relative to the innermost of said members, continuous biasing means between said outermost member and said stop member urging said stop member in one direction, said stop member and said innermost member having a plurality of stop shoulders formed thereon, a rst pair of said shoulders confronting one another for temporarily blocking the axial movement of said plug and socket members after a partial separation, a second pair of said shoulders confronting one another for temporarily blocking the axial movement of said plug and socket members after a further partial separation, said stop member being moved against the biasing means to relatively displace said first shoulders out of confronting blocking relation and being moved by said biasing means upon release to relatively displace said second shoulders out of confronting blocking relation, said stop member having a bent over peripheral flange portion spaced radially outwardly of the outermost member and forming a manual actuating handle for moving said stop member against the biasing means, said biasing means more particularly comprising a coil spring bottomed on said ange portion and on said outermost member, respectively.

6. A retardation means for use with explosion proof separable plug and socket members comprising, a movable latch on one of said members and having two separate latch shoulders, and at least one additional latch shoulder on the other of said members, one pair of said latch shoulders confronting one another to block movement between said members after a rst partial separation and another pair of said latch shoulders confronting one another to block movement between said members after a second partial separation, said latch being movable twice to effect complete separation of the plug and socket members.

JOHN G. HOWARD. PHILIP S. ROCKWELL.

REFERENCES CITED The following references are of rec-crd in the le of this patent:

UNITED STATES PATENTS 

